1. Field of the Invention
The present invention relates to a wireless IC device and to a wireless IC device in which an RFIC (radio frequency integrated circuit) element is mounted on an object including a metal body. The present invention also relates to a clip-shaped RFID (radio frequency identifier) tag and to a clip-shaped RFID tag attachable to and detachable from a conductor of an article. The present invention further relates to an article including an RFID tag such as an article including a conductor and a clip-shaped RFID tag attachable to and detachable from the conductor.
2. Description of the Related Art
If an RFID tag utilizing the UHF band for wireless communications is directly affixed to a metal body, an electric field component of radio waves transmitted from a reader/writer becomes zero on a surface of the tag, making it unable to perform read/write of the tag. Therefore, when an RFID tag is affixed to a metal body, the RFID tag is generally located away from a metal surface.
In this regard, WO 2009/008296 discloses a technique of affixing an RFID tag having a loop antenna with a loop surface thereof perpendicular to a metal surface. This technique enables the RFID tag not only to pick up radio waves but also to utilize the metal surface as a radiation element, so that the RFID tag (wireless IC device) with a large gain is achieved.
According to JP 2004-192287 A, electronic data is stored in a clip clipping a medium to be clipped such as paper. The electronic data is output and input through wireless communications utilizing an RFID. According to JP 2004-307209 A, a notification assisting apparatus includes a first antenna part connected to a receiver, a second antenna part connected to an IC chip reader, and a clip-shaped main body to which these antenna parts are attached. When the notification assisting apparatus is attached to a file and the second antenna part is pivoted, the second antenna part projects downward from the notification assisting apparatus and comes into contact with, or in proximity to, a portion of the file. Transmission and reception between the notification assisting apparatus and an IC chip are smoothly performed through the second antenna part.
However, the structure of WO 2009/008296 including an RFID tag affixed with a loop surface perpendicular to a metal surface causes the RFID tag to project from the metal body and therefore is not suitable for a use particularly requiring robustness of a tag (e.g., for a gas cylinder).
By attaching an RFID tag to a clip as described in JP 2004-192287 A or JP 2004-307209 A the RFID tag can easily be attached to and detached from an object such as a paper document. However, if the object is a conductor, i.e., if the clip is attached to a conductor, the technique of JP 2004-192287 A or JP 2004-307209 A has a problem of not being able to ensure a sufficient communication distance because the conductor impairs the communication characteristics (particularly, the gain) of the RFID tag.